Setting up the dual boot for Windows 10 and Linux Mint 19.2 took longer than expected on my new LG Gram 14 (its a 2018 model). This was the common error error that plagued me for hours when I tried to boot from a start up usb:
Failed to open EFIBootBootExt.efi – Not Found
Failed to load image EFIBootBootExt.efi – Not Found
start_image() returned Not Found
I tried Rufus, UNetbootin, BalenaEtcher and several others. I did the disable secure boot in BIOS, but no avail. In the end, I went back to Rufus, and did realised I did not try the DD (Disk Image) . Once I did that – Viola, I was finally able to boot it from a usb.
Here are some useful links:
My LG Gram uses Phoenix Securecore Technology Setup for BIOS, and it can be a little bit tricky to find where ‘disable secure boot’ is, but this post helped me discover where it was, in the end it wasn’t my issue, but its good to know.
I had UNetbootin stuck on my startup which I didn’t want – here is a useful link for removing it